In this work we present the progress in developing a fibre laser hydrophone array, based on Distributed Bragg Reflector Fibre Laser (DBR-FL), operating in the C telecom band. The goal is to build multiplexed arrays of hydrophones, with an equivalent spectral noise level between 500 Hz and 5 kHz of some 40 dB ref μPa/(Hz)1/2, close to the limit of the Deep Sea State Zero (DSS0). This kind of arrays can be employed in underwater acoustic surveillance of harbours, of maritime areas of strategic relevance, but also in biologic oceanography by surveying marine mammals. The DBR-FL cavity is formed by a short length of single-mode Erbium-doped optical fibre delimited by a high reflection mirror and an output coupler consisting of two fibre Bragg gratings. Any variation of the cavity length and of the effective refractive index n, induced by strain, temperature or pressure, produces a shift of the fibre laser emission wavelength. Different lasers, with different emission wavelengths, can be inscribed on the same fibre and interrogated by the same opto-electronic unit, enabling a quasi-distributed measurement. A preliminary test in marine environment has been made, using an array of two DBR-FL, placed on the same optical cable about 1 m apart. New tests and measurements are in progress, both on single sensor in an equipped pool to characterize their noise equivalent level, and on arrays of a small number (2 to 4) of DBR-FL sensors.

Experimental test of a Fibre Laser Hydrophone Array

BEVERINI, NICOLO';MACCIONI, ENRICO;STEFANI FABIO;
2011-01-01

Abstract

In this work we present the progress in developing a fibre laser hydrophone array, based on Distributed Bragg Reflector Fibre Laser (DBR-FL), operating in the C telecom band. The goal is to build multiplexed arrays of hydrophones, with an equivalent spectral noise level between 500 Hz and 5 kHz of some 40 dB ref μPa/(Hz)1/2, close to the limit of the Deep Sea State Zero (DSS0). This kind of arrays can be employed in underwater acoustic surveillance of harbours, of maritime areas of strategic relevance, but also in biologic oceanography by surveying marine mammals. The DBR-FL cavity is formed by a short length of single-mode Erbium-doped optical fibre delimited by a high reflection mirror and an output coupler consisting of two fibre Bragg gratings. Any variation of the cavity length and of the effective refractive index n, induced by strain, temperature or pressure, produces a shift of the fibre laser emission wavelength. Different lasers, with different emission wavelengths, can be inscribed on the same fibre and interrogated by the same opto-electronic unit, enabling a quasi-distributed measurement. A preliminary test in marine environment has been made, using an array of two DBR-FL, placed on the same optical cable about 1 m apart. New tests and measurements are in progress, both on single sensor in an equipped pool to characterize their noise equivalent level, and on arrays of a small number (2 to 4) of DBR-FL sensors.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/149859
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